1. Field of the Invention
The present invention relates to a liquid crystal display device in which a pixel portion includes a reflective electrode and a transmissive electrode.
2. Description of the Related Art
With the development of the information society, portable information devices such as phones, computers, and digital cameras have been widely used. There are limitations on weight and volume of a portable information device so that the information device can be carried. In particular, the proportion of weight and volume of a battery is high in an information device; thus, the capacity of the battery is limited.
In order to provide a portable information device that can be used for a long time with use of a battery with limited capacity, it is necessary to use components and devices with less power consumption for the portable information device. As an example of the display device with less power consumption, a reflective liquid crystal display device can be given.
A reflective liquid crystal display device has a structure in which a liquid crystal layer is interposed between a transmissive electrode transmitting visible light and a reflective electrode reflecting visible light. In the reflective liquid crystal display device, light which enters the display device from the transmissive electrode side through a film having a polarizing function or the like and is reflected by the reflective electrode is modulated by the liquid crystal layer, so that images are displayed.
Since in the reflective liquid crystal display device, a backlight is not used and display is seen by utilization of external light, power consumption is low. As an example of the reflective liquid crystal display device, a display device in which a reflective electrode is provided with a texture structure formed including a material with a low refractive index and a light-reflecting film formed including a material with a high refractive index is formed thereover has been devised (see Patent Document 1).
However, in the reflective liquid crystal display device, the display is difficult to recognize in some cases in an environment where the amount of external light is small. In view of the above, a so-called semi-transmissive liquid crystal display device has been devised, in which a pixel electrode includes a transmissive electrode and a reflective electrode and which is used as a reflective liquid crystal display device in an environment where sufficient external light can be obtained and used as a transmissive liquid crystal display device using a backlight in an environment where sufficient external light can not be obtained.
However, in the semi-transmissive liquid crystal display device provided with a reflective electrode and a transmissive electrode, the area which reflects external light is smaller as compared with a reflective liquid crystal display device including a pixel electrode provided with only a reflective electrode, and the area which transmits light from a backlight is smaller as compared with a transmissive liquid crystal display device including a pixel electrode provided with only a transmissive electrode. Accordingly, it has a problem in that display is dark.
In order to solve the above problem, a liquid crystal display panel in which a microlens is provided on a surface on the light incidence side has been proposed. In particular, a method is devised in Patent Document 2, in which a microlens is provided by irradiating a photocurable material layer formed on a surface on the light incidence side with light through a liquid crystal display panel so that misalignment is not caused between the microlens and a pixel.